Home – Home – Jornals – Russian Geology and Geophysics 2021 number 10

The Lahroud Ophiolite in northwestern Iran contains extensive zones of Paleozoic ophiolite as remnantsof the Paleo-Tethys oceanic crust. The principal rock units are gabbro overlain by pillowbasalt, which is intruded by granites and interbedded with pelagic sedimentary units including radiolariancherts. Geochemistry and radioisotope studies, supported by Nd, Sm, Sr, and Pb isotope data, indicatethat the Lahroud Ophiolite originates from a within-plate basaltic mantle source. The isotope studiesshow that the basalts are derived from Indian-type oceanic mantle sources. The radiogenic data indicatethe involvement of subduction-related terrigenous materials in the source magma. All the rocks are geochemically cogenetic and were generated by fractionation of a melt with a composition of average E-MORB with a calc-alkaline signature. Two ⁴⁰Ar/³⁹Ar ages, 343 ± 3 Ma for muscovite minerals and 187.7 ± 7.7 Ma for glasses, suggest that metamorphic and basaltic rocks formed during the Late Paleozoic to Early Jurassic, respectively. Microfossil studies show the presence of Paleozoic biostratigraphy. The crystallization process and rifting into the oceanic crust in the Lahroud Ophiolite probably began in the Carboniferous, with volcanic activity continuing during the late Triassic.